1. Field of the Invention
The present invention relates generally to an apparatus and method that provide a three-dimensional sound effect at the time of reproducing a source sound file.
2. Description of the Related Art
Since mobile terminals (a mobile phone, a Personal Digital Assistant (PDA), a Moving Picture Experts Group-1 Audio Layer-3 (MP3) phone, etc.) generally have small sizes, small-sized speakers having low output must be mounted therein even if stereo speakers are employed and the distances between the stereo speakers are short, so that it is difficult to reproduce three-dimensional (3D) sound using the stereo speakers mounted in the mobile terminals, unlike the case where sound is reproduced using headphones or general speakers.
In order to overcome the above-described problem, mobile phones capable of reproducing 3D sound do not reproduce general source sound as 3D sound in real time, but employ a method of containing source sound that was previously produced to exhibit a 3-D effect and reproducing the source sound using stereo speakers mounted in the mobile phones.
However, in accordance with the above method, source sound itself must be previously produced to exhibit a 3D effect when reproduced using normal speakers, so that general source sound that was not produced as 3D sound cannot be reproduced as 3D sound using headphones, and the 3D effect thereof is low even when such source sound is listened to through headphones.
As a result, there is no prior art method that can always reproduce sound in 3D form when the sound is listened to using headphones or speakers.
In particular, spreading is necessary to reproduce 3D sound. In the prior art technology, spreading is performed without differentiation between mono source sound and stereo source sound, so that the effect of spreading applied to the mono source sound is low.
In order to localize sound in an arbitrary 3D space, a Head-Related Transfer Function (HRTF) DataBase (DB) is employed, where the HRTF is modeled on the principle that is used by humans to locate sound. The HRTF DB is a DB in which the transfer mechanisms, through which sounds emitted from various locations around a human are transmitted to the human's eardrum, an entrance to the ear, or other parts of the human's auditory organ, are databased. If source sound having no directionality is processed using the HRTF DB, the sensation of a location can be provided to sound (due to sound localization) to allow a human to feel as if sound were generated from a specific location using a headphone reproduction environment.
However, in general, mobile terminals (a mobile phone, a PDA, an MP3 phone, etc.) do not support a method of localizing sound at a location in a 3D space. Furthermore, since source sound files themselves do not have 3D location information, mobile terminals cannot reproduce sound as if sound entities existed at specific locations in a 3D space in conjunction with the location designation of users or the location and movement path designation of games or graphics or as if sound entities moved along a specific movement path, but simply reproduce sound or reproduce sound after applying simple effects thereto.
Accordingly, even when a user or a game/graphic requires a sound effect that localizes a sound in a 3D space or moves a sound in a mobile terminal environment that supports stereo sound, such a sound effect can be realized.